No, the FOREIGNERS are interfering in U.S. elections = illegal.
I was responding to your comment as “Isn’t this illegal” as the “this” being what X did by identifying where posts are coming from.
Problem with a foreign individuals taking the actions uncovered by X is what can be done? If it could be tied back to a foreign government then the government could impose sanctions, but that hasn’t been proven. Money from foreigners is illegal and a campaign wouldn’t be able to keep it, plus potential penalties. But no law I can think of where the U.S. could act against an individual foreigner.